Spread spectrum coded waveforms in ultrasound diagnostics

ABSTRACT

Techniques, systems, and devices are disclosed for ultrasound diagnostics using spread spectrum, coherent, frequency- and/or phase-coded waveforms. In one aspect, a method includes synthesizing individual orthogonal coded waveforms to form a composite waveform for transmission toward a biological material of interest, in which the synthesized individual orthogonal coded waveforms correspond to distinct frequency bands and include one or both of frequency-coded or phase-coded waveforms; transmitting a composite acoustic waveform toward the biological material of interest, where the transmitting includes transducing the individual orthogonal coded waveforms into corresponding acoustic waveforms to form the composite acoustic waveform; receiving acoustic waveforms returned from at least part of the biological material of interest corresponding to at least some of the transmitted acoustic waveforms that form the composite acoustic waveform; and processing the received returned acoustic waveforms to produce an image of at least part of the biological material of interest.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent document is a continuation of U.S. patent application Ser.No. 16/149,061, filed on Oct. 1, 2018, which is a continuation of U.S.patent application Ser. No. 15/876,081, filed on Jan. 19, 2018, now U.S.Pat. No. 10,085,722, which is a continuation of U.S. patent applicationSer. No. 15/236,229, filed on Aug. 12, 2016, now U.S. Pat. No.9,872,667, which is a continuation of U.S. patent application Ser. No.14/604,612, filed on Jan. 23, 2015, now U.S. Pat. No. 9,420,999, whichis a continuation of U.S. patent application Ser. No. 13/663,100, filedon Oct. 29, 2012, now U.S. Pat. No. 8,939,909, which claims the benefitof priority of U.S. Provisional Patent Application No. 61/553,137, filedon Oct. 28, 2011. The entire contents of the before-mentioned patentapplications are incorporated by reference as part of the disclosure ofthis document.

TECHNICAL FIELD

This patent document relates to systems and processes for ultrasounddiagnostics.

BACKGROUND

Ultrasound imaging is an imaging modality that employs the properties ofsound waves traveling through a medium to render a visual image.Ultrasound imaging has been used as an imaging modality for decades in avariety of biomedical fields to view internal structures and functionsof animals and humans. Ultrasound waves used in biomedical imaging mayoperate in different frequencies, e.g., between 1 and 20 MHz, or evenhigher frequencies. Some factors including inadequate spatial resolutionand tissue differentiation can lead to less than desirable image qualityusing conventional techniques of ultrasound imaging, which can limit itsuse for many clinical applications.

SUMMARY

Techniques, systems, and apparatuses are disclosed for ultrasounddiagnostics using spread spectrum, coherent, frequency- and/orphase-coded waveforms that can exhibit wide instantaneous bandwidth.

In one aspect of the disclosed technology, a method of creating an imagefrom an acoustic waveform in an acoustic imaging device includes settinga transmit/receive switch in the acoustic imaging device into a transmitmode to transmit an acoustic waveform toward a target, in transmittingthe acoustic waveform, synthesizing, in one or more waveformsynthesizers, a plurality of substantially orthogonal coded waveformsthat form a composite waveform as the transmitted acoustic waveformtoward the target, in which each waveform corresponds to a distinctfrequency band and the coded waveforms include at least one offrequency-coded waveforms or phase-coded waveforms, setting thetransmit/receive switch in the acoustic imaging device into a receivemode to receive a returned acoustic waveform that returns from at leastpart of the target, converting the received returned acoustic waveformfrom analog format to digital format as a received composite waveformcomprising information of the target, and processing the receivedcomposite waveform to produce an image of at least part of the target.

In another aspect, an acoustic waveform imaging system is provided toinclude waveform generation unit comprising one or more waveformsynthesizers coupled to a waveform generator, wherein the waveformgeneration unit synthesizes a composite waveform comprising a pluralityof substantially orthogonal coded waveforms corresponding to frequencybands that are generated by the one or more waveform synthesizersaccording to waveform information provided by the waveform generator,the coded waveforms including at least one of frequency-coded waveformsor phase-coded waveforms; a transmit/receive switching unit thatswitches between a transmit mode and a receive mode; an array oftransducer elements in communication with the transmit/receive switchingunit that transmits an acoustic waveform based on the composite waveformtoward a target and receives a returned acoustic waveform returned fromat least part of the target; an array of analog to digital (A/D)converters to convert the received returned acoustic waveform receivedby the array of transducer elements from analog format to digital formatas a received composite waveform comprising information comprisinginformation of the target; a controller unit in communication with thewaveform generation unit and the array of A/D converters comprising aprocessing unit that processes the received composite waveform toproduce an image of at least part of the target; and a user interfaceunit in communication with the controller unit.

In another aspect, a method of creating an image from an acousticwaveform is provided to include setting a transmit/receive switch intotransmit mode; selecting a mode of operation from a plurality ofoperating modes; synthesizing, in one or more waveform synthesizers, aplurality of substantially orthogonal coded waveforms that form acomposite waveform, wherein each waveform corresponds to a distinctfrequency band, the coded waveforms including at least one offrequency-coded waveforms or phase-coded waveforms; transmitting anacoustic waveform based on the composite waveform toward a target;setting the transmit/receive switch into receive mode; receiving areturned acoustic waveform returned from at least part of the target;converting the received returned acoustic waveform from analog format todigital format as a received composite waveform comprising informationof the target; and processing the received composite waveform to producean image of at least part of the target.

In another aspect, a method of creating an image from an acousticwaveform is provided to include combining a plurality of coded waveformscorresponding to different frequency bands to produce a compositewaveform comprising substantially orthogonal wave signals at thedifferent frequency bands, the coded waveforms including at least one offrequency-coded waveforms or phase-coded waveforms; using the compositewaveform to produce an acoustic probe wave that includes the differentfrequency bands toward a target; receiving acoustic energy returned fromat least part of the target after the acoustic probe wave is sent to thetarget; converting the received returned acoustic energy into a digitalcomposite waveform comprising information of the target; and processingthe received composite waveform to produce an image of at least part ofthe target.

In yet another aspect, a device for creating an image from an acousticwaveform is provided to include means for combining a plurality of codedwaveforms corresponding to different frequency bands to produce acomposite waveform comprising substantially orthogonal wave signals atthe different frequency bands, the coded waveforms including at leastone of frequency-coded waveforms or phase-coded waveforms; means forusing the composite waveform to produce an acoustic probe wave thatincludes the different frequency bands toward a target; means forreceiving acoustic energy returned from at least part of the targetafter the acoustic probe wave is sent to the target; means forconverting the received returned acoustic energy into a digitalcomposite waveform comprising information of the target; and means forprocessing the received composite waveform to produce an image of atleast part of the target.

The subject matter described in this patent document can provide one ormore of the following features and be used in many applications. Forexample, the disclosed technology can be used during routine primarycare screenings to identify and locate early stage malignancies, as wellas later stage cancers, which can potentially raise survival rates ofhard to diagnose asymptomatic patients. The disclosed technology can beused by board certified radiologists to diagnose neoplasms as benign ormalignant prior to any surgical biopsy or resection intervention, whichmay also improve patient survival rate while reducing unnecessarybiopsies. The disclosed technology can, when integrated with a fineneedle biopsy instrument, be used in medical procedures to confirmnoninvasive diagnoses, which can reduce the level of invasiveness ofsuch biopsy procedures. The disclosed technology can, when integratedwith minimally invasive surgical high definition video instrumentation,fuse optical and ultrasound images, which can further give surgeonsadded abilities to locate and surgically excise diseased tissue withoutexcising excessive healthy tissue. The disclosed technology can, whenintegrated with specialized surgical instrumentation, fusing ultrasoundimages with other data, can give surgeons added abilities to locate andmanipulate anatomic areas of interest while minimizing unnecessarydamage to nearby structures. The disclosed technology can reduce theamount of time for the brachytherapy treatment of malignant neoplasmsby, for example, precisely guiding the insertion of catheters and sealedradioactive sources into the proper location. Similarly, the disclosedtechnology can aid insertion of high dose, localized pharmaceuticals fortreatments of diseases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a block diagram of an exemplary ultrasound imaging systemusing spread spectrum coded waveforms.

FIG. 1B shows a chart for operation of an exemplary ultrasound imagingsystem using spread spectrum coded waveforms.

FIG. 2 shows a graph of an exemplary spread spectrum, wide instantaneousbandwidth, frequency- and/or phase-coded waveform featuring a pluralityof waveforms.

FIG. 3 shows ambiguity function characteristics of an exemplary spreadspectrum coded waveform.

FIGS. 4A-4C show an exemplary diagram for beam steering, dynamicfocusing, and forming.

FIG. 5 shows an exemplary block diagram for correlation processing of aspread spectrum coded waveform.

Like reference symbols and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Techniques, systems, and apparatuses are described for generating,transmitting, receiving, and processing coherent spread spectrumfrequency- and/or phase-coded waveforms used in ultrasound diagnostics.

Ultrasound imaging can be performed by emitting a time-gated, singlefrequency or narrow instantaneous bandwidth acoustic waveform (pulse),which is partly reflected from a boundary between two mediums (e.g.,biological tissue structures) and partially transmitted. The reflectioncan depend on the acoustic impedance difference between the two mediums.Ultrasound imaging by some techniques may only use amplitude informationfrom the reflected signal. For example, when one pulse is emitted, thereflected signal can be sampled continuously. In biological tissue,sound velocity can be considered fairly constant, in which the timebetween the emission of a waveform and the reception of a reflectedsignal is dependent on the distance the waveform travels in that tissuestructure (e.g., the depth of the reflecting structure). Therefore,reflected signals may be sampled at multiple time intervals to receivethe reflected signals being reflected from multiple depths. Also,different tissues at the different depths can partially reflect theincident waveform with different amounts of energy, and thus thereflected signal from different mediums can have different amplitudes. Acorresponding ultrasound image can be constructed based on depth. Thetime before a new waveform is emitted can therefore be dependent of themaximum depth that is desired to image. Ultrasound imaging techniquesemploying pulsed monochromatic and/or narrow instantaneous bandwidthwaveforms can suffer from poor resolution of image processing andproduction. Yet, waveforms with spread spectrum, wide instantaneousbandwidth characteristics that can be coded (e.g., by frequency and/orphase) can enable real-time control of ultrasound imaging and higherquality resultant images.

FIG. 1A shows a block diagram of an exemplary ultrasound system (100)that can produce acoustic waveforms with enhanced waveform propertiesthat include a spread-spectrum, wide instantaneous bandwidth, coherency,pseudo-random noise characteristics, and frequency- and/or phase-coding.System (100) can be configured in one of many system designs. In oneexample, system (100) can include a Master Clock (101) for timesynchronization. The Master Clock (101) can be interfaced with a SystemController (102). System Controller (102) can include a processing unit,e.g., a central processing unit (CPU) of RISC-based or other types ofCPU architectures. System Controller (102) can also include at least oneinput/output (I/O) unit(s) and/or memory unit(s), which are incommunication with the processing unit, to support various functions ofthe System Controller (102). For example, the processing unit can beassociated with a system control bus, e.g., Data & Control Bus (103).System Controller (102) can be implemented as one of various dataprocessing architectures, such as a personal computer (PC), laptop,tablet, and mobile communication device architectures.

The memory unit(s) can store other information and data, such asinstructions, software, values, images, and other data processed orreferenced by the processing unit. Various types of Random Access Memory(RAM) devices, Read Only Memory (ROM) devices, Flash Memory devices, andother suitable storage media can be used to implement storage functionsof the memory unit(s). The memory unit(s) can store pre-stored waveformsand coefficient data and information, which can be used in theimplementation of generating a waveform, e.g., such as aspread-spectrum, wide instantaneous bandwidth, coherent, pseudo-randomnoise, and frequency and/or phase-coded waveform. The memory unit(s) canstore data and information obtained from received and processedwaveforms, which can be used to generate and transmit new waveforms. Thememory unit(s) can be associated with a system control bus, e.g., Data &Control Bus (103).

The I/O unit(s) can be connected to an external interface, source ofdata storage, and/or display device. The I/O unit(s) can be associatedwith a system control bus, e.g., Data & Control Bus (103). Various typesof wired or wireless interfaces compatible with typical datacommunication standards, such as but not limited to Universal Serial Bus(USB), IEEE 1394 (FireWire), Bluetooth, IEEE 802.111, Wireless LocalArea Network (WLAN), Wireless Personal Area Network (WPAN), WirelessWide Area Network (WWAN), WiMAX, IEEE 802.16 (Worldwide Interoperabilityfor Microwave Access (WiMAX)), and parallel interfaces, can be used toimplement the I/O unit. The I/O unit can interface with an externalinterface, source of data storage, or display device to retrieve andtransfer data and information that can be processed by the processorunit, stored in the memory unit, or exhibited on an output unit.

System Controller (102) can control all of the modules of system (100),e.g., through connection via Data & Control Bus (103). For example, Data& Control Bus (103) can link System Controller (102) to one or moreattached digital signal processors, e.g., Digital Signal Processor(104), for processing waveforms for their functional control. DigitalSignal Processor (104) can include one or many processors, such as butnot limited to ASIC (application-specific integrated circuit), FPGA(field-programmable gate array), DSP (digital signal processor), AsAP(asynchronous array of simple processors), and other types of dataprocessing architectures. Data & Control Bus (103) can also link SystemController (102), as well as Digital Signal Processor (104), to one ormore display units with modules for user interfaces, e.g., Display (105)with a module User Interface (106) to provide information to a user oroperator and to receive input/commands from the user or operator.Display (105) can include many suitable display units, such as but notlimited to cathode ray tube (CRT), light emitting diode (LED), andliquid crystal display (LCD) monitor and/or screen as a visual display.Display (105) can also include various types of display, speaker, orprinting interfaces. In other examples, Display (105) can include otheroutput apparatuses, such as toner, liquid inkjet, solid ink, dyesublimation, inkless (such as thermal or UV) printing apparatuses andvarious types of audio signal transducer apparatuses. User Interface(106) can include many suitable interfaces including various types ofkeyboard, mouse, voice command, touch pad, and brain-machine interfaceapparatuses.

The exemplary system (100) can include Waveform Generator (107), whichcan be controlled by System Controller (102) for producing one or moredigital waveforms. The one or more digital waveforms can be generated asanalog electronic signals (e.g., analog waveforms) by at least oneelement in an array of waveform synthesizers and beam controllers, e.g.,represented in this example as Waveform Synthesizer and Beam Controller(108). Waveform Generator (107) can be at least one of a functiongenerator and an arbitrary waveform generator (AWG). For example,Waveform Generator (107) can be configured as an AWG to generatearbitrary digital waveforms for Waveform Synthesizer and Beam Controller(108) to synthesize as individual analog waveforms and/or a compositeanalog waveform. Waveform Generator (107) can also include at least onememory unit(s) that can store pre-stored waveforms and coefficient dataand information used in the generation of a digital waveform.

The exemplary system (100) shown in FIG. 1A includes WaveformSynthesizer and Beam Controller (108) comprising I number of arrayelements. In one example, Waveform Synthesizer and Beam Controller (108)can be configured to include at least one waveform synthesizer elementon each line of the I number of array waveform synthesizers. In anotherexample, Waveform Synthesizer and Beam Controller (108) can include atleast one beam controller element on each line of the I number of arraybeam controllers. In another example, Waveform Synthesizer and BeamController (108) can include at least one waveform synthesizer elementand beam controller element on each line of the I number of arraywaveform synthesizers and beam controllers. Waveform Synthesizer andBeam Controller (108) can include a phase-lock loop system forgeneration of an electronic signal, e.g., a radio frequency (RF)waveform. An exemplary RF waveform can be synthesized by WaveformSynthesizer and Beam Controller (108) from individual waveformsgenerated in the array elements of Waveform Synthesizer and BeamController (108), e.g., one individual RF waveform can be generated inone array element substantially simultaneously to all other individualwaveforms generated by the other array elements of Waveform Synthesizerand Beam Controller (108). Each individual RF waveform can be definedfor a particular frequency band, also referred to as a frequencycomponent or ‘chip’, and the waveform properties of each individualwaveform can be determined by Waveform Generator (107), which caninclude at least one amplitude value and at least one phase valuecorresponding to the chip. Waveform Generator (107) can issue commandsand send waveform data including information about each individualwaveform's properties to Waveform Synthesizer and Beam Controller (108)for generation of individual RF waveforms that can be composited into acomposite RF waveform.

The individual RF waveforms and/or the composite RF waveform generatedby Waveform Synthesizer and Beam Controller (108) can be modified byOutput Amplifiers (109), which includes an array of I number ofamplifiers, e.g., by amplifying the gain and/or shifting the phase of awaveform. Output Amplifiers (109) can be used as transducer drivers. Theindividual RF waveforms and/or the composite RF waveform can be passedto Transmit/Receive (T/R) switch (110), e.g., an N-pole double-throwtransmit/receive switch. T/R Switch (110) that can be interfaced with atransducer module. A generated RF waveform, e.g., the composite RFwaveform and/or at least one individual RF waveform, that is to betransmitted into a target medium can be transduced into, for example, anacoustic wave by the transducer module that can include an array oftransducer elements, e.g., Transducer Array (111) comprising I number ofelements. For example, the transduced acoustic wave can be emitted inthe form of an acoustic waveform pulse. Each array element of theTransducer Array (111) may generate one or more acoustic waveforms thatcorrespond to the individual waveform chips determined by the WaveformGenerator (107).

The exemplary transduced transmitted acoustic waveform can betransmitted toward a target area, e.g., biological tissue, and form aspatially combined acoustic waveform. The transmitted waveform canpropagate into the target medium, which for example, can have one ormore inhomogeneous mediums that partially transmit and partially reflectthe transmitted acoustic waveform. Exemplary acoustic waveforms that arepartially reflected, also referred to as returned acoustic waveforms,can be received by Transducer Array (111). For example, each arrayelement of I array elements of Transducer Array (111) can be configuredto receive a returned acoustic waveform corresponding to the frequencychip and convert it to an analog RF waveform. The individual received(analog) RF waveforms can be modified by Pre-Amplifier module (112),which includes an array of I number of amplifiers, e.g., by amplifyingthe gain and/or shifting the phase of a waveform. The individualreceived waveforms can be converted from analog format to digital formatby analog to digital (A/D) Converter module (113), which includes anarray of I number of A/D converters. A/D Converter module (113) caninclude A/D converters that have low least significant bit (LSB) jitter,spurious-free dynamic range (SFDR) and waveform dependency, such thatthe exemplary waveforms can be adequately decoded. The converted digitalrepresentations of the individual received waveforms can be processed bya processor, e.g., Digital Signal Processor (104), in manner thatcreates and forms a representative image of the target medium.

The exemplary system (100) can be operated in one of many operationmodes. In one example, Master Clock (101) can provide the time base forsynchronizing the system (100), e.g., as a time base for the WaveformSynthesizers (108). Master Clock (101) can be configured as a low phasenoise clock such that the exemplary waveforms can be phase encoded. Anoperator can select the mode of operation at User Interface (106).Exemplary modes of operation provided for the user to select at the UserInterface (106) include Conventional A-Mode (e.g., 1D Depth only image),Conventional B-Mode (e.g., 2D Plane image—transverse vs. depth),Conventional C-Mode (e.g., 2D Plane image at selected depth), andConventional D-Modes (e.g., Doppler Modes). Exemplary Doppler modesinclude Color Doppler (e.g. superposition of color coded Doppler andB-mode images), Continuous Doppler (e.g., 1D Doppler profile vs. depth),Pulsed Wave Doppler (e.g., Doppler vs. time for selected volume), andDuplex/Triplex Doppler (e.g., superposition of Conventional B-Mode,Conventional C-Mode or Color Doppler, and Pulsed Wave Doppler). Someother exemplary modes of operations can include Conventional 3D and 4D(“real time” 3D) volume renderings of the previously described modes ofoperations. The exemplary system (100) can implement new modes ofoperation that can generate spread spectrum, wide instantaneousbandwidth, frequency- and/or phase-coded waveforms. For example, a usercan select exemplary ATS-Modes (Artificial Tissue Staining Modes) thatcan comprise a B-Mode, a C-Mode, a D-Mode, or other mode combined withimage color coding to aid tissue differentiation—analogous to tissuestaining for microscopic histological studies; and exemplary CAD-Modes(Computer Aided Diagnostic Modes) that differentiate and identify tissuetype. ATS-Modes can employ the use of features for image color coding inimage processing based on one or more of a number of measured propertiesthat are obtained from the returned echo waveform from the target area,e.g., the returned echo from an exemplary transmitted spread spectrum,wide instantaneous bandwidth, coded acoustic waveform. CAD-Modes can useclassifiers (algorithms) to classify, for example, tissue types based onfeatures of the measured properties of the returned echo from the targetarea, e.g., the returned echo from an exemplary spread spectrum, wideinstantaneous bandwidth, coded acoustic waveforms. The featuresproperties can include differing impedances, amplitude reflections (as afunction of wavelength), group delay, etc. Some exemplary classifiersthat can be employed using CAD-Modes can include deterministicclassifiers, stochastic classifiers (e.g., Bayesian classifiers), andneural network classifiers.

FIG. 1B shows an exemplary operation process (150) for operating thesystem (100) for ultrasound imaging. For each time epoch, process (150)can begin by implementing process (151) to switch system (100) intransmit mode. For example, the System Controller (102) can command anN-pole double-throw T/R switch, e.g., T/R Switch (110), to transmitposition. Process (150) includes a process (152) to check a user-definedmode of operation. For example, mode of operation can be selected by auser using User Interface (106), or the mode of operation can beselected by another entity or internally within system (100). Based onthe selected operation mode, System Controller (102) can commandWaveform Generator (107) to issue a digital message (data) to one ormore elements in Waveform Synthesizers and Beam Controllers (108) thatdefines the frequency, amplitude and phase of each of the frequencychips that form a desired wideband composite RF waveform commanded,e.g., implemented in a process (153). Process (152) can occur anywhereand implemented in multiple instances during process (150). Process(150) includes a process (153) to issue waveform data (e.g., theexemplary digital message/data) to waveform synthesizers and beamformers, such as the Waveform Synthesizers and Beam Controllers (108).The issued waveform data can include the frequency, amplitude and phaseinformation of the desired frequency chips that are synthesized asfrequency- and/or phase-coded waveforms, in which each coded waveformcorresponds to a distinct frequency band. Process (150) includes aprocess (154) to generate individual analog RF waveforms that correspondto defined frequency chips. For example, each element in the array ofWaveform Synthesizers and Beam Controllers (108) can convert the digitalmessage/data from the Waveform Generator (107) into individual analogwaveforms that can make up a coherent analog wideband compositewaveform. Process (150) includes a process (155) to amplify theindividual analog waveforms that can make up a coherent analog widebandcomposite waveform. For example, each analog waveform and/or widebandcomposite waveform can be amplified by an array element in OutputAmplifier (109). The amplified analog wideband composite waveform canthen pass through the T/R Switch (110) and excite its respective arrayelement of the Transducer Array (111) (e.g., in an ultrasound probe).Process (150) includes a process (156) to transduce the composite analogwaveform to an acoustic waveform that can propagate throughout thescanned volume. For example, each element of the Transducer Array (111)can provide an acoustic waveform from each of the individual analogwaveform corresponding to the frequency chip generated in WaveformSynthesizer and Beam Controller (108) that makes up the widebandcomposite acoustic waveform. Transducer Array (111) can form theacoustic beam that propagates into the target medium, e.g., biologicaltissue volume under study.

At the end of process (156), process (150) can implement process (157)to switch system (100) in receive mode. For example, the SystemController (102) can command the N-pole double-throw T/R Switch (110) toreceive position. Process (150) includes a process (158) to receive areturned acoustic waveform, which can be in the form of one or morereturned acoustic waveforms (also referred to as acoustic waveformechoes). Process (158) can also include transducing the returnedacoustic waveform echo(es) into individual received analog waveforms,e.g., corresponding to the frequency chips of the generated individualwaveforms. For example, the returned acoustic waveform propagates backto and is received by Transducer Array (111). Each element of TransducerArray (111) can convert the received acoustic waveform it receives intoan analog signal (waveform). Process (150) includes a process (159) toamplify the individual received analog waveforms. For example, eachreceived analog waveform can be amplified by its respective low noisepre-amplifier element in Pre-Amplifier module (112). Process (150)includes a process (160) to convert the individual received analogwaveforms into digital waveform data. For example, each received (andamplified) analog waveform signal can be converted into a digital wordby each respective A/D element in A/D Converter module (113). Thedigital format data can be sent to Digital Signal Processor (104) forsignal processing. Process (150) includes a process (161) to process thedigital waveform data into image frames representative of the targetmedium. Process (161) can also include compositing the digital waveformdata into a composite digital signal representing the individual andcomposite received analog waveform. For example, Digital SignalProcessor (104) can detect the amplitude and phase of each of thefrequency chips that comprise the wideband composite acoustic waveformreceived by each of the transducer array elements. Digital SignalProcessor (104) can form the received beam and separate the amplitudeand Doppler components of each resolution element of the beam, and canform an image frame associated with mode previously selected byoperator. The image frame formed by Digital Signal Processor (104) canbe displayed on Display (105) to the user. For other subsequent timeepochs, System Controller (102) can repeat this exemplary process, e.g.,by commanding Waveform Generator (107) to issue to each element inWaveform Synthesizers (108) another digital message that defines theamplitude and phase of each of the frequency chips that comprise thewideband composite waveform and by commanding T/R Switch (110) back totransmit position, etc.

The system (100) can be implemented to produce spread-spectrum, wideinstantaneous bandwidth (e.g., up to 100% or more of fractionalbandwidth), coherent, pseudo-random noise (PRN), frequency- and/orphase-coded waveforms for ultrasound imaging. There are limitlessembodiments of such waveforms. One example is featured in FIG. 2 , whichshows an exemplary plot of a generated composite waveform (200) that iscomprised of a plurality of individual waveforms (e.g., frequencychips). In some implementations, the individual waveforms of thecomposite waveform (200) can be PRN waveforms including a sequence ofpulses for each frequency chip that repeats itself after a sequence orcode period (T), e.g., such that the sequence has a very low correlationwith any other sequence in the set of frequency chips, or with the samesequence at a significantly different time frame, or with narrow bandinterference or thermal noise. For example, the system (100) cangenerate exactly the same sequences of the exemplary PRN waveforms atboth the transmitter and the receiver ends, so a received signalsequence (based on the transmitted signal sequence) can exhibit a highcorrelation for signal processing to produce an acoustic image of thetarget.

As shown in FIG. 2 , an exemplary individual waveform or chip (201) ofthe composite waveform (200) corresponds to the frequency chip f_(N−2)that is transmitted during a transmit period T beginning at time framet₀, e.g., as described in the process (156) in FIG. 1B. As shown in FIG.2 , following the transmit period T, a receive time interval T_(R) isexhibited, in which returned acoustic waveform echoes are received asdescribed in the process (158) in FIG. 1B. The transmit period T and thereceive time interval T_(R) form a frame period T_(f), which can berepeated in subsequent time frames (t₁, t₂, t₃, . . . ).

The exemplary composite waveform (200) can be represented by an equationfor waveform, W, which can be represented in the time domain as acomplex number, given by Equation (1):

$\begin{matrix}{{W(t)} = {\sum\limits_{k}{\sum\limits_{n}{A_{n}e^{j{({{2\pi\;{nf}_{0}t} + \Phi_{nk} + C_{n}})}}{U\left( {t - {kT}_{f}} \right)}}}}} & (1)\end{matrix}$

W is comprised of M individual orthogonal waveforms (e.g., orthogonalfrequency chips), where j=−√{square root over (−1)}. In Equation (1), Trepresents the chip duration or period of the coded sequence, and f₀represents the fundamental chip frequency, such that f₀=1/NT, and inwhich Nf₀ is the maximum frequency and (M−N+1)f₀ is the minimumfrequency. n represents a sequence of positive integers from N−M+1 to N.The waveform repetition frequency is 1/T_(f), with T_(f) being theduration of a frame or epoch, and U(x)=1 for 0≤x≤T_(f). Φ_(nk)represents the frequency chip phase term of the n^(th) chip in thek^(th) time epoch, and A_(n) is the amplitude of the n^(th) chip. Thefrequency chip phase term Φ_(nk) can be a pseudo-random phase term, inwhich a pseudo-randomly scrambled starting phase Φ_(nk) is a randomnumber in the set {I_(nk)2π/N}, where I_(nk) is a sequence of random,positive integers selected without replacement from the series I=0, 1,2, 3, . . . , N, with N being a large number. C_(n), which is anadditive phase term, is a number between 0 and 2π. For example, thefrequency chip phase pseudo-random values Φ_(nk) can be pre-stored in anexemplary database within a memory unit of System Controller (102)and/or Waveform Generator (107).

The composite waveform, W, can be formed by synthesizing substantiallyorthogonal coded waveforms (e.g., frequency chips), in which each codedwaveform corresponds to a distinct frequency band, and the codedwaveforms includes at least one of frequency-coded waveforms orphase-coded waveforms, e.g., the coded waveforms synthesized in theWaveform Synthesizers (108). The coded waveforms can be synthesized asfrequency-coded waveforms by selecting two or more frequencies thatdefine the carrier frequencies of the frequency chips (e.g., includingselecting the minimum and maximum frequency) and determining the A_(n)amplitude values of the frequency chips. The synthesis of thefrequency-coded can also include determining a time-bandwidth product(Mf₀T) parameter of each waveform of the coded waveforms. In someimplementations, the amplitude for a particular frequency chip can bedetermined as a single value for that frequency chip during a particulartime epoch and repeated in subsequent time epochs for the particularfrequency chip. In other implementations, the amplitude for a particularfrequency chip can be determined as a single value for that frequencychip during a particular time epoch and assigned a different singlevalue in subsequent time epochs for the particular frequency chip. Andin other implementations, the amplitude for a particular frequency chipcan be determined to include multiple amplitude values for thatfrequency chip during a particular time epoch, in which the multiplevalues of the A_(n) can be repeated or varied in subsequent time epochsfor the particular frequency chip. The selection of the range offrequencies from the maximum frequency (Nf₀) to the minimum frequency((M−N+1)f₀) plus the set of individual waveform amplitude terms (A_(n))can utilize one of many known code sequences (e.g. including pushingsequences, Barker Codes, etc.) or, for example, utilize a numericalsearch on pseudo-random codes or any other codes for minimum ambiguitysidelobes.

The coded waveforms can additionally or alternatively be synthesized asphase-coded waveforms by determining individual waveform phase terms(Φ_(nk)) of each waveform of the coded waveforms. For example, toprovide variation of the composite waveform, W, the phase Φ_(nk) caninclude one or more phase values for a frequency chip within thetransmit period T. In some implementations, the phase Φ_(nk) for aparticular frequency chip can be determined as a single value for thatfrequency chip during a particular time epoch and repeated in subsequenttime epochs for the particular frequency chip. In other implementations,the phase Φ_(nk) for a particular frequency chip can be determined as asingle value for that frequency chip during a particular time epoch andassigned a different single value in subsequent time epochs for theparticular frequency chip. And in other implementations, the phaseΦ_(nk) for a particular frequency chip can be determined to includemultiple values for that frequency chip during a particular time epoch,in which the multiple values of the Φ_(nk) can be repeated or varied insubsequent time epochs for the particular frequency chip. For example,the waveform (201) in the first time epoch (t₀) can include a firstphase Φ_(A), for example, as its phase shift for the beginning portionof the transmit period T and a second phase Φ_(B), for example, as itsphase shift for the latter portion of the transmit period T. Thewaveform (201) in the next time epoch (t₁) can repeat the exemplaryphases Φ_(A) and Φ_(B) as its beginning and latter phase shifts orinclude another phase shift sequence (e.g., such as Φ_(A), Φ_(B), Φ_(C),or such as Φ_(B) and Φ_(A), or other configurations). The synthesis ofthe frequency-coded can also include determining a time-bandwidthproduct (Mf₀T) parameter of each waveform of the coded waveforms.

An exemplary transmitted waveform, W, can be comprised of the set of Mindividual waveforms that are orthogonal and completely span thefrequency range f_(N−M+1) to f_(N), as seen in FIG. 2 . The parameter Ncan be chosen to be a large number to give W a wide instantaneousbandwidth. In the special case when the lowest frequency f_(N−M+1)=1/T,then W can describe any wideband waveform that may be contained withinthis range of frequencies. For any waveform among the M individualwaveforms, one or more phases (e.g., Φ_(nk)) can be encoded in a singlewaveform during the interval T. Additionally, any waveform among the Mindividual waveforms can include multiple amplitudes encoded in a singlewaveform. This can be implemented by amplitude weighting and phaseweighting.

The family of individual waveforms described by Equation (1) can form acoherent, pseudo-random noise, frequency- and/or phase-coded, spreadspectrum composite waveform. Based on the selection of parameters, theindividual waveforms can be made to be statistically orthogonal to anydegree desired. For example, the sidelobe levels of the ambiguityfunction, described later in Equation (2), for a given waveformrepresents the degree of orthogonality of that waveform. By determiningparticular parameters of the waveforms, medical ultrasound imageresolution can be significantly improved. For example, parameters thataffect the resolution of medical ultrasound images include thetime-bandwidth product (Mf₀T) parameter, which determines the inherentcombined axial range (e.g., Doppler resolution) and the specklereduction ability of the waveform, and the individual waveform phaseterms (Φ_(nk)), which determine the statistical degree of orthogonality,e.g., which in turn determines the degree that the waveform can functionin inhomogeneous media of biological tissues. For example, the lower thesidelobes, the greater the orthogonality and greater the resolution(less noise). The selection of the set of individual waveform phaseterms (Φ_(nk)) can utilize one of many known code sequences (e.g.including Barker, Frank, Golay, etc.) or, for example, utilize anumerical search on pseudo-random codes or any other codes for minimumambiguity sidelobes.

In some implementations, the composite waveform (200), e.g., describedby Equation (1), can be a single wideband, coherent, frequency- and/orphase-coded waveform. For example, based on the selection of parameters,the single waveform can be made to be statistically orthogonal to anyother signal waveform or noise signal present in the target medium.

The parameter A_(n), which is the amplitude of the n^(th) chip, andC_(n), which is an additive phase term, in combination can providepre-emphasis of the analog signal that excites each individual elementof Transducer Array (111) to produce a transmitted acoustic waveformthat has the desired amplitude and phase characteristics over thefrequency range of W. Pre-emphasis of the transmitted waveform cancompensate for both the non-constant amplitude and phase response oftransducer elements as a function of frequency, and the non-uniformpropagation characteristics of intervening tissue layers. For example,the pre-emphasis terms can provide an acoustic waveform that has equalamplitude chips with constant (e.g., flat) amplitude and a known phaseversus frequency characteristic. Such constant amplitude versusfrequency acoustic waveforms can be referred to as ‘white’ waveforms.Alternatively, if pre-emphasis is not provided, then the transmittedacoustic waveform can replicate the frequency response of thetransducer, and such waveforms are referred to as ‘colored’ waveforms.De-emphasis of the received waveform can permit determination of thereflection characteristic of the target medium's volume, e.g.,biological tissue volume.

By inspection, single frequency modes (e.g., Conventional A-, B- andC-Mode), due to their monochromatic nature, do not need pre-emphasis.Such single frequency waveforms may require amplitude control, forexample, to ensure biologically safe sound intensity limits.

If the phase of each chip is random, the transmitted waveform, W, canhave random noise-like characteristics. If the phases (Φ_(nk)+C_(n)) ofeach chip are uniquely determined, repeatable and synchronized to theMaster Clock (as shown in FIG. 1A), the transmitted waveform, W, can beclassified as pseudo-random noise. Such pseudo-random noise waveformsare coherent permitting implementation of coherent receivers.

Image processing advantages of wide instantaneous bandwidth,pseudo-random noise waveforms can include reduction, with properwaveform selection, and potential elimination of speckle, e.g.,speckles/speckle patterns, which are random intensity patterns producedby the mutual interference waveforms, which are commonly associated withconventional medical ultrasound images. This exemplary reduction inspeckle can be an analogous comparison of a scene illuminated by wideband, Gaussian noise-like white light, which has no observable speckleto narrow band laser illumination with exhibits strong speckle of thesame scene.

Signal processing advantages of coherent, pseudo-random noise,frequency- and phase-coded waveforms can include waveforms having verylow time and Doppler sidelobes. For example, an ambiguity function,A(τ,υ), can be a two-dimensional representation that shows thedistortion of a received waveform processed by a matched filter in thereceiver due to the effect of Doppler shift (υ) or propagation delay(τ). Specifically, the exemplary ambiguity function A(τ,υ) is defined byEquation (2) and is determined solely by the waveform properties and thereceiver characteristics and not by the scenario. The ambiguity functionof A(τ,υ) is defined by

$\begin{matrix}{{{A\left( {\tau,v} \right)} = {\int\limits_{- \infty}^{+ \infty}{{X_{a}(t)}{X_{b}^{*}\left( {t - \tau} \right)}e^{j\; 2\pi\;{vt}}}}}{{{{where}\mspace{14mu}{X_{k}(t)}} = {\frac{1}{\sqrt{T}}e^{j{\lbrack{{2\pi\;{f_{k}{({t - t_{k}})}}} + \Phi_{k}}\rbrack}}}},{{{for}\mspace{14mu} 0} \leq t \leq T},{{X_{k}(t)} = {0\mspace{14mu}{{otherwise}.}}}}} & (2)\end{matrix}$

For waveforms of the type described by Equation (1), the followingequation can be obtained:

$\begin{matrix}{{A\left( {\tau,v,t,f_{n},\Phi_{n},f_{m},\Phi_{m},T} \right)} = {\left( {1 - \frac{{\tau - \left( {\Delta\; t} \right)}}{T}} \right)\frac{{Sin}\left\lbrack {2{\pi\left( {\Delta\; f} \right)}\left( {T - {{\Delta\; t}}} \right)} \right\rbrack}{\left\lbrack {2{\pi\left( {\Delta\; f} \right)}\left( {T - {{\Delta\; t}}} \right)} \right\rbrack}e^{j\; 2{\pi{\lbrack{{\Delta\;{f{({T + {\Delta\; t}})}}} - {f_{n}\Delta\; t} + {vt} + {\Delta\Phi}}\rbrack}}}}} & (3)\end{matrix}$where Δt=τ−t, Δf=υ−(f_(n)−f_(m)), and ΔΦ=Φ_(n)−Φ_(m), which can resultin the complete ambiguity equation shown in Equation (4):

$\begin{matrix}{{x\left( {\tau,v} \right)} = {\frac{1}{M}{\sum\limits_{n}{\sum\limits_{m}{A\left( {\tau,v,t,f_{n},\Phi_{n},f_{m},\Phi_{m},T} \right)}}}}} & (4)\end{matrix}$where both n and m are a sequence of positive integers from N−M+1 to N.

FIG. 3 shows exemplary ambiguity function characteristics of apseudo-random noise, frequency-coded waveform (301), represented by anequation for waveform, W. The exemplary coded waveform (301) includes acode length of 128. As shown in FIG. 3 , the sidelobes (302) of thisambiguity function are due to chip-to-chip phase interactions and have aplateau level below the peak that is a function of N².

By inspection, many waveforms (W) are possible depending on the specificrandom number codes (I_(nk)) selected. However, the sidelobe performancecannot be guaranteed for every waveform defined, and therefore onlythose codes which give sufficiently low sidelobes as determined by anumerical search of a set of possible codes should be used.

For example, in medical ultrasound applications, living tissue as apropagation medium is inhomogeneous. Propagation medium inhomogeneitycan introduce differential time delays, and living tissue can introduceunwanted motion induced Doppler. Ultrasound transducer arrays also canhave undesirable side lobes and grating lobes (e.g., due to physicalsize limitations) in the off axis portions of ultrasound beam that addunwanted time delay and Doppler returns to the returns of the main lobe.Waveforms that exhibit low ambiguity function sidelobes cansignificantly improve focusing and target contrast due through thereduction interference from differential time delays, motion inducedDoppler, transducer side lobe effects.

Coherent pseudo-random noise, frequency- and/or phase-coded waveformscan enable higher order cross range focusing techniques to be employedthat can improve the lateral resolution of size limited ultrasoundtransducer arrays, e.g., medical ultrasound transducer arrays.

For example, each biological tissue type and each diseased tissue typesmay exhibit their own unique ultrasound echo return as a function offrequency and spatial morphology. Using conventional Elastograph-Mode(E-Mode) modalities, it can be difficult to take advantage of suchproperties to classify tissues, e.g., due to measurement errors such asthe inability to accurately characterize the ultrasound wave propagationthrough overlaying inhomogeneous media. Exemplary waveforms produced bythe exemplary system (100), e.g., wide instantaneous bandwidth, coherentpseudo-random noise, frequency- and/or phase-coded waveforms, can enabletissue differentiation by simultaneously determining the propagationdelay for each acoustic ray through intervening tissue layers andaccurately determining the spatial echo features of the target volumeunder investigation. Classifiers, one example being Bayesian inferenceClassifiers among others, can be applied to the feature data obtainedfrom the measured characteristics of the received echo to automaticallyclassify tissue types observed in the target volume providing a ComputerAided Diagnostic-Mode (CAD-Mode).

Unlike conventional E-Modes, which inherently have significantly reducedimage quality and rely on individual operator technique, the exemplarywaveforms described by Equation (1) can inherently provide improvedimage quality while simultaneously colorizing the resultant image bytissue type in the ATS and/or CAD-Modes. With this advantage, usertechnique can be mitigated and the margins of a lesion are discerniblethus permitting improved diagnoses.

In addition, Waveform Synthesizers (108) positioned on transmit andDigital Signal Processor (104) positioned on receive (as shown in FIG.1A), can also perform beam control (e.g., beam steering, dynamic beamfocusing, and beam forming) functions. FIGS. 4A-4C show the basics ofthese digital electronic functions by introducing a differential timedelay, or equivalently a phase shift, and amplitude weighting betweeneach of the elements of the phased array. As can be seen in FIG. 4A, thedifferential phase shift can compensate for the differential change indistance (d) each acoustic ray (r₁, r₂, . . . r_(i), . . . ) travelsfrom i^(th) element to the point of focus (p). An angle (θ) is formed asthe point of focus (p) is not along the z-axis direction of directaim/alignment of the Transducer Array (111) toward a target in thetarget medium. Additionally, a differential amplitude weight can beapplied to each element to control the beam shape and suppress side andgrating lobes. Also, for one or more chips in an exemplary waveform,Waveform Generator (107) can pre-encode a phase delay to delay the phaseof the one or more chips transmitted at each transducer element inTransducer Array (111). An exemplary result of this feature can be seenin FIGS. 4B and 4C. The exemplary phase delay values for the one or morechips can be communicated to Digital Signal Processor (104) and/orSystem Controller (102) to incorporate the phase delay values in thesignal processing of the received composite waveform.

For narrow instantaneous bandwidth ultrasound devices, this function canbe accomplished by introducing phase shift and amplitude attenuation onthe composite analog signal driving each element. However, for theexemplary spread-spectrum, wide instantaneous bandwidth, frequency- andphase-coded waveforms generated by system (100), each individual chip ofthe waveform (W_(i)) is individually amplitude weighted (B_(ni)) andphase weighted (D_(ni)) as a function of frequency (n) for each arrayelement (i) individually for all I elements, as indicated by Equation(5).

$\begin{matrix}{{W_{i}(t)} = {\sum\limits_{k}{\sum\limits_{n}{A_{n}B_{ni}e^{j{({{2\pi\;{nf}_{0}t} + \Phi_{nk} + C_{n} + D_{ni}})}}{U\left( {t - {kT}_{f}} \right)}}}}} & (5)\end{matrix}$

On transmit, the amplitude and phase weighting required of each chip canbe computed by the System Controller (102) and can be sent as aninstruction to the Waveform Generator (107). Waveform Generator (107)can then send the digital words (real and imaginary components) to theWaveform Synthesizers and Beam Controller (108) that produces the analogdrive signal that is amplified by Amplifier (109) and sent to eachelement of the array of Transducer Array (111).

On receive, the reverse process takes place. The A/D Converter module(113) can send the digital words that represent the amplitude and phaseinformation of each chip for each array element to the Digital SignalProcessor (104), which in turn can digitally form the receive beam foreach chip.

A multitude of ways can be used to process the received waveforms, e.g.,wide-bandwidth, spread-spectrum, frequency and/or phase-coded waveforms.FIG. 5 shows an exemplary correlation processing technique. For example,an input to the exemplary correlation processing technique can include adigitized received signal, Y_(i)(τ,υ), which can be multiplied by thecomplex conjugate replica of the transmitted digital waveform,W_(i)*(τ). The complex conjugate replica W_(i)*(τ) can be time shiftedby 1·τ₀ prior to multiplication. This multiplication operation can berepeated multiple times for multiple time shifts, e.g., J times, as seenin FIG. 5 . The multiple multiplication operations for the multiple timeshifts can be repeated in parallel, but for each operation the replicais shifted in time by an increment, τ₀, from the previous one, as shownin the figure. For each time step, the resultant products can befiltered with a window function, such as a Hann, Hamming, Tukey, KaiserBessel, Dolph-Chebyshev, Blackman-Harris window, etc., a fast FourierTransform (FFT) integrator, and passed through a digital filter. Forexample, a digital filter of a type that is dependent of the specificwaveform, W, can be employed to filter and decimate the inputted signal.The exemplary process can result in the range-Doppler return for eachindividual i^(th) element of the transducer array. The output datastream from the exemplary detection algorithm can then be processedusing conventional techniques to form an image for display. Theprocessed range and Doppler data and/or waveforms can be furtherprocessed by partitioning the I number of transducer elements into twoor more subarrays. The processed range-Doppler return for the i^(th)element can be weighted in amplitude and/or phase depending on whichsubarray that i^(th) element belongs. These weighted returns can then besummed and differenced. These sum and differences can then be processedto improve the cross range image resolution of the system.

Several applications and uses of the disclosed technology can beimplemented to exploit the described features of the aforementionedsystems, methods, and devices. Some examples are described for clinicaluse of the disclosed technology.

In one exemplary application, the resultant image quality, the ATS andCAD modes of an exemplary spread spectrum ultrasound device can enablethe primary care physician to incorporate this modality into a routineexamination screening protocol to locate early stage malignancies (e.g.,Stage 0 or 1), as well as later stage cancers. As the result of thisapplication, the device can potentially, for example, enhance thesurvival rate of hard to diagnose asymptomatic patients suffering fromsuch malignancies such as stomach, pancreatic, bladder cancers, etc.

In another exemplary application, the resultant image quality, ATS andCAD modes of an exemplary spread spectrum ultrasound device can permitboard certified radiologists to diagnose neoplasms as benign ormalignant prior to any surgical biopsy or resection intervention. As aresult of this application, the ability of radiologists to locate anddiagnose early stage malignancies (e.g., Stage 0 or 1) can potentiallyimprove patient survival rate. Additionally, unnecessary biopsies canpotentially be avoided, along with their attendant risk of hard to treator even lethal complications such as, for example, methicillin resistantStaphylococcus aureus (MRSA staph) infections.

In another exemplary application, the resultant 3D image quality of anexemplary spread spectrum ultrasound device and its 4D imagingcapability can be used in fine needle biopsy and other medicalprocedures. For example, the exemplary spread spectrum ultrasound devicecan be integrated into an exemplary fine needle biopsy instrument (e.g.,with the device's transducer probe), which can permit the fine needlebiopsy of very small, early stage (e.g., Stage 0 or 1) neoplasms toconfirm noninvasive diagnoses. As a result of this application, theability of surgeons to avoid open biopsies and the potential for hard totreat and lethal complications that may result is clearly beneficial tothe patient.

In another exemplary application, the integration of this device'sspread spectrum transducer probe with minimally invasive surgical highdefinition video instrumentation can permit the fusing of the opticaland ultrasound images. Given the improved 3D image quality of thisspread spectrum ultrasound device, its 4D imaging capability, the ATSand CAD modes, such fused video and ultrasound images can give surgeonsthe added ability to locate and surgically excise diseased tissuewithout excising excessive healthy tissue.

In another exemplary application, given the improved 3D image quality ofthis spread spectrum ultrasound device, its 4D imaging capability, andits ATS modes, an exemplary spread spectrum ultrasound device can reducethe amount of time for the brachytherapy treatment of malignantneoplasms by precisely guiding the insertion of catheters and sealedradioactive sources into the proper location. The application of thisspread spectrum ultrasound device to brachytherapy can be especiallyuseful for the treatment of small, hard to locate neoplasms and theirmargins.

In another exemplary application, given the improved 3D image quality ofthis spread spectrum ultrasound device, its 4D imaging capability, andits ATS modes, an exemplary spread spectrum ultrasound device can enablethe effective insertion of high dose, localized pharmaceuticaltreatments of diseases by precisely guiding the insertion of cathetersand pharmaceuticals into the proper location. The application of thisspread spectrum ultrasound device to brachytherapy can be especiallyuseful for the treatment of small, hard to locate neoplasms.

Implementations of the subject matter and the functional operationsdescribed in this specification, such as various modules, can beimplemented in digital electronic circuitry, or in computer software,firmware, or hardware, including the structures disclosed in thisspecification and their structural equivalents, or in combinations ofone or more of them. Implementations of the subject matter described inthis specification can be implemented as one or more computer programproducts, e.g., one or more modules of computer program instructionsencoded on a tangible and non-transitory computer readable medium forexecution by, or to control the operation of, data processing apparatus.The computer readable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter affecting a machine-readable propagated signal, or a combinationof one or more of them. The term “data processing apparatus” encompassesall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, or acombination of one or more of them.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, suchas, for example, digital signal processors (DSP), and any one or moreprocessors of any kind of digital computer. Generally, a processor willreceive instructions and data from a read only memory or a random accessmemory or both. The essential elements of a computer are a processor forperforming instructions and one or more memory devices for storinginstructions and data. Generally, a computer will also include, or beoperatively coupled to receive data from or transfer data to, or both,one or more mass storage devices for storing data, e.g., magnetic,magneto optical disks, or optical disks. However, a computer need nothave such devices. Computer readable media suitable for storing computerprogram instructions and data include all forms of non volatile memory,media and memory devices, including by way of example semiconductormemory devices, e.g., EPROM, EEPROM, and flash memory devices. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any invention or of what may beclaimed, but rather as descriptions of features that may be specific toparticular embodiments of particular inventions. Certain features thatare described in this patent document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A method for acoustic imaging, comprising:producing a composite waveform having a plurality of individual codedwaveforms each corresponding to distinct frequency bands, wherein theproducing of the composite waveform includes: generating a set of randomnumbers, selecting individual composite digital codes based on thegenerated set of random numbers, wherein each of the individualcomposite digital codes correspond to the individual coded waveforms indigital format, and forming the composite waveform from the selectedindividual coded waveforms; producing and transmitting a compositeacoustic beam, based on the generated composite waveform, toward amaterial of interest, wherein the transmitting includes generating drivesignals corresponding to the composite waveform to drive transducerelements of a transducer array to form the composite acoustic beam;receiving returned acoustic waveforms that are returned from at leastpart of the material of interest corresponding to at least sometransmitted acoustic waveforms that form the composite acoustic beam;and processing the received returned acoustic waveforms to produce animage containing information of the material of interest.
 2. The methodof claim 1, wherein the generated set of random numbers includes randomphases.
 3. The method of claim 1, further comprising: storing theselected individual composite digital codes in memory of one or morecomputer devices.
 4. The method of claim 1, wherein the selectedindividual coded waveforms include coherent waveforms.
 5. The method ofclaim 1, wherein the selected individual coded waveforms includefrequency-coded waveforms.
 6. The method of claim 1, wherein theselected individual coded waveforms include phase-coded waveforms. 7.The method of claim 1, wherein at least one of the selected individualcoded waveforms that form the composite waveform includes two or moreamplitudes, two or more phases, or two or more amplitudes and two ormore phases.
 8. The method of claim 1, wherein at least some of theselected individual coded waveforms that form the composite waveform areindividually amplitude weighted, thereby providing at least one ofsteering, focus, or forming of the composite acoustic beam.
 9. Themethod of claim 1, wherein at least some of the selected individualcoded waveforms that form the composite waveform are individually phaseweighted, thereby providing at least one of steering, focus, or formingof the composite acoustic beam.
 10. An acoustic imaging system,comprising: a computing device comprising a processor and a memory andconfigured to produce a composite waveform having a plurality ofindividual coded waveforms each corresponding to distinct frequencybands, wherein the computing device is operable to produce the compositewaveform by: generating a set of random numbers, selecting individualcomposite digital codes based on the generated set of random numbers,wherein each of the individual composite digital codes correspond to theindividual coded waveforms in digital format, and forming the compositewaveform from the selected individual coded waveforms; a digital toanalog (D/A) converter, in communication with the computing device, toconvert the individual coded waveforms that form the composite waveformfrom the digital format to an analog format as an analog compositewaveform; an array of transducer elements, in communication with the D/Aconverter, to receive the analog composite waveform and transmit acomposite acoustic beam toward a material of interest, wherein the arrayof transducer elements are operable to receive a returned acousticwaveform returned from at least part of the material of interest; and ananalog to digital (A/D) converter, in communication with the array oftransducer elements, to convert the received returned acoustic waveformreceived by the array of transducer elements from an analog format to adigital format as a received composite waveform comprising informationof the material of interest.
 11. The system of claim 10, wherein thearray of transducers are configured to acoustically couple to areceiving volume containing the material of interest, and wherein atransmission of the composite acoustic beam by the array of transducerelements includes generating drive signals corresponding to thecomposite waveform that drive the transducer elements of the array tocreate and propagate the composite acoustic beam in the receiving volumeand toward the material of interest.
 12. The system of claim 10, whereinthe computing device includes a controller unit and a user interfaceunit in communication with the controller unit, wherein the controllerunit is configured to process the received composite waveform to producean image of at least part of the material of interest and display theimage on the user interface.
 13. The system of claim 10, wherein thegenerated set of random numbers generatable by the computing deviceincludes random phases.
 14. The system of claim 10, wherein thecomputing device is configured to store the selected individualcomposite digital codes in the memory.
 15. The system of claim 10,wherein the selected individual coded waveforms include coherentwaveforms.
 16. The system of claim 10, wherein the selected individualcoded waveforms include frequency-coded waveforms.
 17. The system ofclaim 10, wherein the selected individual coded waveforms includephase-coded waveforms.
 18. The system of claim 10, wherein at least oneof the selected individual coded waveforms that form the compositewaveform includes two or more amplitudes, two or more phases, or two ormore amplitudes and two or more phases.